The actinomycete Lentzea aerocolonigenes produces the antitumor antibiotic rebeccamycin. In previous studies the rebeccamycin production was significantly increased by the addition of glass beads during cultivation in different diameters between 0.5 – 2 mm and the induced mechanical stress by the glass beads was proposed to be responsible for the increased production. Thus, this study was conducted to be a systematic investigation of different parameters for macroparticle addition, such as bead diameter, concentration and density (glass and ceramic) as well as shaking frequency, for a better understanding of the particle induced stress on L. aerocolonigenes. The induced stress for optimal rebeccamycin production can be estimated by a combination of stress energy and stress frequency. In addition, the macroparticle-enhanced cultivation of L. aerocolonigenes was combined with soy lecithin addition to further increase the rebeccamycin concentration. With 100 g L-1 glass beads in a diameter of 969 µm and 5 g L-1 soy lecithin a concentration of 388 mg L 1 rebeccamycin was reached after 10 days of cultivation, which corresponds to the highest rebeccamycin concentrations achieved in shake flask cultivations of L. aerocolonigenes stated in literature so far.
Serology testing for COVID-19 is important in evaluating active immune response against SARS-CoV-2, studying the antibody kinetics, and monitoring reinfections with genetic variants and new virus strains, in particular, the duration of antibodies in virus-exposed individuals and vaccine-mediated immunity. In this work, recombinant S protein of SARS-CoV-2 was expressed in Rachiplusia nu, an important agronomic plague. One gram of insect larvae produces an amount of S protein sufficient for 150 determinations in the ELISA method herein developed. We established a rapid production process for SARS-CoV-2 S protein that showed immunoreactivity for anti-SARS-CoV-2 antibodies and was used as a single antigen for developing the ELISA method with high sensitivity (96.2%) and specificity (98.8%). Our findings provide an efficient and cost-effective platform for large-scale S protein production, and the scale-up is linear, thus avoiding the use of complex equipment like bioreactors.
In this work, we applied online chlorophyll a fluorescence measurements to monitor the changes in the photochemical parameters both in nitrate-deplete and nitrate-replete cultures of Nannochloropsis oceanica, in addition to biochemical parameters such as growth, lipid, fatty acid, and pigment contents. Under nitrate-replete conditions, growth was promoted along with pigment content, while total lipid content and fatty acid saturation level diminished. Under nitrate-deplete conditions, cultures showed an increased de-epoxidation state of the xanthophyll cycle pigments. Fast transients revealed a poor processing efficiency for electron transfer beyond QA, which was in line with the low electron transport rate due to nitrate depletion. Lipid content and the de-epoxidation state were the first biochemical parameters triggered by the change in nutrient status, which coincided with a 20% drop in the online effective quantum yield of PSII (ΔF/Fm’), and a raise in the Vj measurements. A good correlation was found between the changes in ΔF/Fm’ and lipid content (r=-0.96, p<0.01). The results confirm the reliability and applicability of online fluorescence measurements to monitor lipid induction in N. oceanica.
Molecular diagnosis is an essential means to detect pathogens. The portable nucleic acid detection chip has excellent prospects in places where medical resources are scarce, and it is also of research interest in the field of microfluidic chips. Here, the paper developed a new type of microfluidic chip for nucleic acid detection where stretching acts as the driving force. The sample entered the chip by applying capillary force. The strain valve was opened under the action of tensile force, and the spring pump generated the power to drive the fluid to flow to the detection chamber in a specific direction. The detection of COVID-19 was realized on the chip. The RT-LAMP amplification system was adopted to observe the liquid color in the detection chamber to decide whether the sample tested positive or negative qualitatively.
Adoptive cell immunotherapy with chimeric antigen receptor (CAR) T cell has brought a revolutionary means of treatment for aggressive diseases such as hematologic malignancies and solid tumors. Over the last decade, FDA approved three types of CAR-T cells against CD19 hematologic malignancies, including Tisagenlecleucel (Kymriah), Axicabtagene ciloleucel (Yescarta), and Brexucabtagene autoleucel (Tecartus). Despite outstanding results gained from different clinical trials, CAR-T cell therapy is not free from side effects and toxicities, and needs careful investigations and improvements. Gene-editing technology, clustered regularly interspaced short palindromic repeats (CRISPR)/ CRISPR-associated protein 9 (Cas9) system has emerged as a promising tool to address some of the CAR-T therapy hurdles. Using CRISPR/Cas9 technology, CAR expression as well as other cellular pathways can be modified in various ways to enhance CAR-T cell’s anti-tumor function and persistence in immunosuppressive tumor microenvironment. CRISPR/Cas9 technology can also be utilized to reduce CAR-T cells toxicity and side effects. Hereby, we discuss the practical challenges and hurdles related to the accuracy, efficiency, efficacy, safety and delivery of CRISPR/Cas9 technology to the genetically engineered-T cells. Combining of these two state-of-the-art technologies, CRISPR/Cas9 and CAR-T cells, the field of oncology has an extraordinary opportunity to enter a new era of immunotherapy, which offers novel therapeutic options for different types of tumors.
Since 2014, an Asian lineage of Zika virus has caused outbreaks, and it has been associated with neurological disorders in adults and congenital defects in newborns. The resulting threat of the Zika virus to human health has prompted the development of new vaccines, which have yet to be approved for human use. Vaccines based on the attenuated or chemically inactivated virus will require large-scale production of the intact virus to meet potential global demands. Intact viruses are produced by infecting cultures of susceptible cells, a dynamic process that spans from hours to days and has yet to be optimized. Here, we infected Vero cells adhesively cultured in well-plates with two Zika virus strains: a recently isolated strain from the Asian lineage, and a cell-culture-adapted strain from the African lineage. At different time points post-infection, virus particles in the supernatant were quantified; further, microscopy images were used to quantify cell density and the proportion of cells expressing viral protein. These measurements were performed across multiple replicate samples of one-step infections every four hours over 60 hours and for multi-step infections every four to 24 hours over 144 hours, generating a rich dataset. For each set of data, mathematical models were developed to estimate parameters associated with cell infection and virus production. The African-lineage strain was found to produce a 14-fold higher yield than the Asian-lineage strain in one-step growth and a 7-fold higher titer in multi-step growth, suggesting a benefit of cell-culture adaptation for developing a vaccine strain. We found that image-based measurements were critical for discriminating among different models, and different parameters for the two strains could account for the experimentally observed differences. An exponential-distributed delay model performed best in accounting for multi-step infection of the Asian strain, and it highlighted the significant sensitivity of virus titer to the rate of viral degradation, with implications for optimization of vaccine production. More broadly, this work highlights how image-based measurements can contribute to discrimination of virus-culture models for the optimal production of inactivated and attenuated whole-virus vaccines.
The most effective way to prevent and control infectious disease outbreak is through vaccines. The increasing use of vaccines has elevated the need to establish new manufacturing strategies. One of the major approaches is cell-based production, which creates a need for high cell density to enable higher cell production levels. This has led to development of the technology of cell carriers, including micro and macro cell carriers. To follow the production process, quantifying the number of cells on these carriers is required, as well as the tracking of their viability and proliferation. However, owing to various carriers’ unique structures, tracking the cell’s is challenging using current traditional assays that were originally developed for monolayers of adherent cells. The current “gold standard” method is counting cell nuclei, separating cells from the carrier, staining with crystal violet and visually counting under a microscope. This method is tedious and counts both live and dead cells. A few other techniques were developed but were specific to the carrier type and involved specialized equipment. In this study, we describe a broadly ranging method for counting cells on carriers that was developed and employed as part of the production of a vaccine for use in the SARS-CoV-2 pandemic. The method is based on the Alamar blue dye, a well-known, common marker for cell activity, and was found to be successful in tracking cell adsorption, cell growth and viability on carriers. No separation of the cells from the carriers is needed, nor is any specialized equipment; the method is simple and rapid, and provides comprehensive details necessary for process control of viral vaccine production in cells. This method can be easily implemented in any of a number of cell-based processes and other unique platforms for measuring growth of encapsulated cells.
Luminescence, a physical phenomenon that producing cool light in vivo, has been found in bacteria, fungi and anminals but not yet in terrestrial higher plants. Through genetic engineering, it is feasible to introduce luminescence system into living plant cells as biomarkers. Recently, some plants transformed with luminescent systems can glimmer in darkness, which can be observed by our naked eyes and provide a novel lighting resource. In this review, we summarized the development of luminescence in plant cells, followed by exampling the successful cases of glowing plants transformed with diverse luminescent systems. The potential key factors to optimize a glowing plant are also discussed. Our review is useful for the creation of the optimized glowing plants, which can be used not only in scientific research, but also as promising substitutes of artificial light sources in the future.
Predicting the fate of a microbial population (i.e., growth, gene expression…) remains a challenge, especially when this population is exposed to very dynamic environmental conditions, such as those encountered during continuous cultivation. Indeed, the dynamic nature of continuous cultivation process implies the potential deviation of the microbial population involving genotypic and phenotypic diversification. This work has been focused on the induction of the arabinose operon in Escherichia coli as a model system. As a preliminary step, the GFP level triggered by an arabinose-inducible ParaBAD promoter has been tracked by flow cytometry in chemostat with glucose-arabinose co-feeding. For a large range of glucose-arabinose co-feeding, the simultaneous occurrence of GFP positive and negative subpopulation was observed. In a second set of experiments, continuous cultivation was performed by adding either glucose or arabinose, based on the ability of individual cells for switching from low GFP to high GFP states, according to a technology called segregostat. In segregostat mode of cultivation, on-line flow cytometry analysis was used for adjusting the arabinose/glucose transitions based on the phenotypic switching capabilities of the microbial population. This strategy allowed finding an appropriate arabinose pulsing frequency, leading to a prolonged maintenance of the induction level with limited impact on phenotypic diversity for more than 60 generations. This result suggests that constraining individual cells into a given phenotypic trajectory is maybe not the best strategy for directing cell population. Instead, allowing individual cells switching around a predefined threshold seems to be a robust strategy leading to oscillating, but predictable, cell population behavior.
Commercial production of therapeutic proteins using mammalian cells requires complex process solutions, and consistency of these process solutions is critical to maintaining product titer and quality between batches. Inconsistencies between process solutions prepared at bench and commercial scale may be due to differences in mixing time, temperature, and pH which can lead to precipitation and subsequent removal via filtration of critical solution components such as trace metals. Pourbaix diagrams provide a useful tool to model the solubility of trace metals and were applied to troubleshoot the scale-up of nutrient feed preparation after inconsistencies in product titer were observed between bench- and manufacturing-scale batches. Pourbaix diagrams modeled the solubility of key metals in solution at various stages of the nutrient feed preparation and identified copper precipitation as the likely root cause of inconsistent media stability at commercial scale. Copper precipitation increased proportionally with temperature in bench-scale preparations of nutrient feed and temperature was identified as the root cause of copper precipitation at the commercial scale. Additionally, cell culture copper titration studies performed in bench-scale bioreactors linked copper-deficient mammalian cell culture to inconsistent titers at the commercial scale. Pourbaix diagrams can predict when trace metals are at risk of precipitating and can be used to mitigate risk during the scale-up of complex media preparations.
Enzymatic detachment of cells might damage important features of cells and could affect subsequent function of cells in various applications. Therefore, non-enzymatic cell detachment using thermosensitive polymer matrix is necessary for maintaining cell quality after harvesting. In this study, we synthesized thermosensitive PNIPAm-co-AAc-b-PS and PNIPAm-co-AAm-b-PS copolymers and LCST was tuned near to body temperature. Then, polymer solutions (5% w/v, 10% w/v, and 20% w/v) were spin coated to prepare films for cell adhesion and thermal-induced cell detachment. The apha-step analysis and SEM image of the films suggested that the thickness of the films depends on the molecular weight and concentration which ranged from 206 nm to 1330 nm for PNIPAm-co-AAc-b-PS and 97.5 nm to 497 nm for PNIPAm-co-AAm-b-PS. The contact angles of the films verified that the polymer surface was moderately hydrophilic at 37°C. From cell attachment and detachment studies, RAW264.7 cells, were convincingly proliferated on the films to a confluent of >80 % within 48 days. However, relatively more cells were grown on PNIPAm-co-AAm-b-PS (5%w/v) films and thermal-induced cell detachment was more abundant in this formulation. As a result, commercial cytodex 3 microcarrier was coated with PNIPAm-co-AAm-b-PS (5%w/v) and interestingly enhanced cell detachment with preserved potential of recovery was observed at low temperature during 3D culturing. Thus, surface modification of microcarriers with PNIPAm-co-AAm-b-PS could be vital strategy for non-enzymatic cell dissociation and able to achieve adequate number of cells with maximum cell viability, and functionality for various cell-based applications. Keywords: surface coated microcarriers; thermosensitive polymer; non-enzymatic cell detachment
Acidithiobacillus ferrooxidans are acidophilic chemolithoautotrophs that are commonly reported to exhibit diauxic population growth behavior where ferrous iron is oxidized before elemental sulfur when both are available, despite the higher energy content of sulfur. We have discovered sulfur dispersion formulations that enables sulfur oxidation before ferrous iron oxidation. The oxidation of dispersed sulfur can lower the culture pH within days below the range where aerobic ferrous iron oxidation can occur so that ferric iron reduction occurs which had previously been reported over extended incubation periods with untreated sulfur. Therefore, we demonstrate that this substrate utilization pattern is strongly dependent on the cell loading in relation to sulfur concentration, sulfur surface hydrophobicity, and the pH of the culture. Our dispersed sulfur formulation, lig-sulfur, can be used to support the rapid antibiotic selection of plasmid-transformed cells, which is not possible in liquid cultures where ferrous iron is the main source of energy for these acidophiles. Furthermore, we find that media containing lig-sulfur supports higher production of green fluorescent protein (GFP) compared to media containing ferrous iron. The use of dispersed sulfur is a valuable new tool for the development of engineered A. ferrooxidans strains and it provides a new method to control iron and sulfur oxidation behaviors.
A robust monoclonal antibody (mAb) bioprocess requires physiological parameters such as temperature, pH, or dissolved oxygen (DO) to be well-controlled as even small variations in them could potentially impact the final product quality. For instance, pH substantially affects N-glycosylation, protein aggregation and charge variant profiles, as well as mAb productivity. However, relatively less is known about how pH jointly influences product quality and titer. In this study, we investigated the effect of pH on culture performance, product titer and quality profiles by applying longitudinal multi-omics profiling, including transcriptomics, proteomics, metabolomics and glycomics, at three different culture pH set points. The subsequent systematic analysis of multi-omics data showed that pH set points differentially regulated various intracellular pathways including intracellular vesicular trafficking, cell cycle, and apoptosis, thereby resulting in differences in specific productivity, product titer and quality profiles. In addition, a time-dependent variation in mAb N-glycosylation profiles, independent of pH was identified to be mainly due to the accumulation of mAb proteins in the endoplasmic reticulum (ER) over culture time, disrupting cellular homeostasis. Overall, this multi-omics-based study provides an in-depth understanding of the intracellular processes in mAb-producing CHO cell line under varied pH conditions and could serve as a baseline for enabling the quality optimization and control of mAb production.
Seasonal influenza infection waves occur both in northern and southern hemispheres every year. Despite the differences in influenza virus surface antigens and virulence of seasonal subtypes, manufacturers are well-adapted to respond to this periodical vaccine demand. Due to decades of influenza virus research, the development of new influenza vaccines is relatively straight-forward. Nevertheless, compared to the recent Covid-19 pandemic where a vaccine is not yet available, influenza vaccine manufacturing would be a major bottleneck for the rapid supply of billions of doses required worldwide. In particular, egg-based vaccine production would be difficult to schedule and shortages of other egg-based vaccines with high demands also have to be anticipated. Cell culture-based production systems enable manufacturing of large amounts of vaccines within a short time frame and expand significantly our options to respond to pandemics and emerging viral diseases. In this work, we present an integrated process for the production of inactivated influenza A virus vaccines based on a MDCK suspension cell line cultivated in a chemically defined medium. Very high titers of 3.6 log10(HAU/100 µL) were achieved using fast growing MDCK cells at concentrations up to 9.5 × 106 cells/mL infected with influenza A/PR/8/34 H1N1 virus in 1 L stirred tank bioreactors. A combination of two membrane-based chromatography steps enabled full recovery for the virus capture and up to 80 % recovery for the virus polishing step, respectively. Purified virus particles showed a homogenous size distribution around a mean diameter of 80 nm. Based on a monovalent dose of 15 µg hemagglutinin (SRID assay), the level of total protein was 58 µg and the level of host cell DNA contamination was below 10 ng. Furthermore, all process steps can be fully scaled up to industrial quantities for commercial manufacturing of either seasonal or pandemic influenza virus vaccines. Fast production of up to 300 vaccine doses per liter within 4 to 5 days makes this process competitive not only to other cell-based processes, but to egg-based processes as well.
Mucociliary clearance is a crucial event that supports the elimination of inhaled particles, bacteria, pollution and hazardous agents from the human airways, and it also limits the diffusion of aerosolized drugs into the airway epithelium. In spite of its relevance, few in vitro models sufficiently address the cumulative effect of the steric and interactive barrier function of mucus on the one hand, and the dynamic mucus transport imposed by ciliary mucus propulsion on the other hand. Here, ad hoc mucus models of physiological and pathological mucus are combined with magnetic artificial cilia to model mucociliary transport in both physiological and pathological states. The Lego®-like concept adopted, in this study, enables the development of mucociliary clearance models with high versatility, since these can be easily modified to reproduce phenomena characteristic of healthy and diseased human airways, while allowing to determine the effect of each parameter and/or structure separately on the overall mucociliary transport. These Lego®-like airway models can be available off-the-shelf because they are exclusively made of readily available materials, thus ensuring reproducibility across different laboratories.
This paper presents the development and testing of a low-cost (< $60), portable, electrical impedance based microflow cytometer for single cell analysis under controlled oxygen microenvironment. The system is based on an AD5933 impedance analyzer chip, a microfluidic chip, and an Arduino microcontroller operated by a custom Android application. A representative case study on human red blood cells (RBCs) affected by sickle cell disease is conducted to demonstrate the capability of the cytometry system. An equivalent circuit model of a suspended biological cell is used to interpret the electrical impedance of single flowing RBCs. RBCs exhibit decreased mean membrane capacitance by 24% upon hypoxia treatment while the mean cytoplasmic resistance remains consistent. RBCs affected by sickle cell disease exhibit decreased cytoplasmic resistance and increased membrane capacitance upon hypoxia treatment. Strong correlations are identified between the changes in the cells’ subcellular electrical components and the hypoxia-induced cell sickling process. The results reported in this paper suggest that the developed method of testing demonstrates the potential application for low-cost screening technique for sickle cell disease and other diseases in the field and low-resource settings. The developed system and methodology can be extended to analyze cellular response to hypoxia in other cell types.
In vitro gut model systems permit the growth of gut microbes outside their natural habitat and are essential to the study of gut microbiota. Systems available today are limited by lack of scalability and flexibility in mode of operation. Here we describe the development of a versatile bioreactor module capable of sensing and controlling of environmental parameters such as pH control of culture medium, rate of influx and efflux of the culture medium, and aerobic/anaerobic atmosphere. Modules can be linked in series to construct a model of a digestive tract to allow the growth of microbiota in vitro. We tested the growth of a model bacterial community in a simulated mammalian gut model. The model attained and maintained a stable bacterial community that metabolized bile acids. The findings illustrate the utility of the model to grow to culture a mixed bacterial community and recapitulate biological activities such as bile acid metabolism in vitro.
Fungal pathogens cause extensive plant diseases that damage crop production in the agricultural industry, resulting in annual crop loss, diminished food security, and historically significant epidemics. Though effective fungicides are available, their risks to the environment and animal health have increased the demand for more sustainable methods to control fungal pathogens. In plants, polygalacturonic-inhibiting proteins (PGIPs) play critical roles for resistance to fungal disease by inhibiting the pectin-depolymerizing activity of endopolygalacturonases (PGs), one type of enzyme secreted by pathogens that compromise plant cell walls and leave the plant susceptible to disease. Here, the interactions between PGIPs from Phaseolus vulgaris (PvPGIP1 and PvPGIP2) and PGs from Aspergillus niger (AnPG2), Botrytis cinerea (BcPG1, BcPG2), and Fusarium moniliforme (FmPG3) were reconstituted through a yeast two hybrid (Y2H) system to investigate the inhibition efficiency of various PvPGIP1 and 2 truncations and mutants. We found that tPvPGIP2_5-8, which contains LRR5 to LRR8 and is of only one-third the size of the full-length peptide, exhibits the same level of interactions with AnPG and BcPGs as the full length PvPGIP2 via Y2H. The inhibitory activities of tPvPGIP2_5-8 on the growth of A. niger were then examined and confirmed on pectin agar. Application of both full length PvPGIP2 and tPvPGIP2_5-8 clearly slows down the growth of A. niger and B. cinerea in the presence of pectin. The investigation on the sequence-function correlation of PvPGIP2 suggests that LRR5 could have the most essential structural feature for the inhibitory activities, and may be a possible target for the future engineering of PGIP with enhanced activity. This work highlights the potential of using plant-derived PGIPs as an exogenously applied fungal control agent both to plants and postharvest crops while minimally impacting the environment and human health.